A review on mass spectrometry-based quantitative proteomics: Targeted and data independent acquisition

- A step-by-step guide to develop quantitative SRM assay for proteomics.
- Tutorials to the selection of protein targets, proteotypic peptides and corresponding SRM transitions.
- Demonstrative applications of SRM in basic biological research and clinical biomarker studies.
- Brief summary of emerging pseudo-SRM (pSRM) and data independent acquisition (DIA) approaches in proteomics.

Mass spectrometry (MS) based proteomics have achieved a near-complete proteome coverage in humans and in several other organisms, producing a wealth of information stored in databases and bioinformatics resources. Recent implementation of selected/multiple reaction monitoring (SRM/MRM) technology in targeted proteomics introduced the possibility of quantitatively follow-up specific protein targets in a hypothesis-driven experiment. In contrast to immunoaffinity-based workflows typically used in biological and clinical research for protein quantification, SRM/MRM is characterized by high selectivity, large capacity for multiplexing (approx. 200 proteins per analysis) and rapid, cost-effective transition from assay development to deployment. The concept of SRM/MRM utilizes triple quadrupole (QqQ) mass analyzer to provide inherent reproducibility, unparalleled sensitivity and selectivity to efficiently differentiate isoforms, post-translational modifications and mutated forms of proteins. SRM-like targeted acquisitions such as parallel reaction monitoring (PRM) are pioneered on high resolution/accurate mass (HR/AM) platforms based on the quadrupole-orbitrap (Q-orbitrap) mass spectrometer. The expansion of HR/AM also caused development in data independent acquisition (DIA). This review presents a step-by-step tutorial on development of SRM/MRM protein assay intended for researchers without prior experience in proteomics. We discus practical aspects of SRM-based quantitative proteomics workflow, summarize milestones in basic biological and medical research as well as recent trends and emerging techniques.

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